Lamp simulator + guide
Morse Code with Light: Flashlight, Blinking and SOS
Any light that switches on and off can send Morse code: a flashlight, a phone, a ship's signal lamp, or your own eyes. Type a message below to flash it on the lamp, then learn how to signal SOS with a flashlight, how to blink Morse, and the true story of the man who blinked a word on television.
The lamp flashes the message at the speed you set (light Morse is normally sent at 5–8 WPM) with a tone so you can hear and see the rhythm together. Turn your phone's volume down if you only want the light.
How to communicate with a flashlight in Morse code
Light Morse follows the same rules as sound Morse: a short flash is a dot, a flash three times longer is a dash, and the dark gaps between them are one unit inside a letter, three between letters and seven between words. The difference is speed. The ear can follow 20 words per minute; the eye cannot. Signal lamps are worked at about 5 to 8 WPM, which means a dot of roughly 150–250 milliseconds and a dash of half a second to three quarters. When in doubt, go slower and make your dashes obviously long.
- Use the switch, or cover the lens. A flashlight with a firm click switch works; so does holding it on and blocking the beam with your palm. Never wave the light to make a "dash": the receiver sees movement, not timing.
- Aim and hold steady. Point directly at the receiver. At night a small LED is visible for miles if it is aimed well.
- Exaggerate the gaps. A clear pause between letters is the most common thing beginners forget. Count "one-two-three" in the dark between letters.
- Send short words. SOS, OK, HELP, YES, NO. Long sentences are tiring for both sides.
- Watch for a reply. By convention the receiver answers with a single dash (or the letter T) to mean "received"; a series of short flashes means "say again".
Using your phone's flashlight
A phone's torch is bright and the screen button is easy to tap, but most phones add a small delay when toggling the LED, so keep the speed low. A trick that works everywhere: open a plain white screen at full brightness and cover and uncover the phone with your hand, or use the lamp simulator above held up to a window. Our SOS page has the pattern ready to go.
How to signal SOS with a flashlight
SOS is ...---..., sent as one unbroken pattern: three short flashes, three long flashes, three short flashes. Then a pause, then again. There are no letter gaps inside SOS, which is what makes it instantly recognizable even if your timing is rough.
- Point the light at the receiver
Aim the flashlight directly at the person or vessel and keep it steady. Cover the lens with your hand or use the switch; do not wave the light around.
- Three short flashes
Three quick flashes of about half a second each, with half-second gaps. That is the letter S.
- Three long flashes
After a short pause, three flashes about three times as long (one and a half seconds each). That is the letter O.
- Three short flashes again
S again. You have sent ··· ––– ··· as one continuous pattern.
- Pause and repeat
Wait five to ten seconds and send it again. Keep repeating until you see a reply or help arrives.
Morse code with your eyes
How to blink SOS in Morse code
Eyes can only close and open, so blinking Morse uses the same trick as a flashlight: a quick blink is a dot and a long, deliberate closed-eye blink is a dash.
Short, normal blinks, evenly spaced. The letter S.
Close your eyes for about a second each time. The letter O.
S again. Pause, then repeat the whole pattern.
Blinking is the slowest form of Morse and the hardest to read, so keep it to very short words and make the long blinks unmistakably long. Spelling out a whole word by eye, as in the story below, takes real concentration from both people. If you are trying to signal distress silently in a room, SOS by blinking is recognized by far more people than any other pattern, which is exactly why it is worth knowing. Note that "three blinks" on its own is not a Morse signal; three short blinks is the letter S, and it only becomes SOS with the three long blinks in the middle.
The man who blinked "torture" on TV
In 1966, US Navy Commander Jeremiah Denton had been a prisoner of war in North Vietnam for almost a year when he was forced to take part in a televised interview intended as propaganda. While answering the interviewer's questions in a flat, cooperative voice, Denton blinked his eyes in Morse code, pretending to be bothered by the studio lights: - --- .-. - ..- .-. ., T-O-R-T-U-R-E. The footage was broadcast in the United States, and naval intelligence read the message. It was the first confirmation that American prisoners were being tortured. Denton was released in 1973 and later served as a US senator from Alabama.
Navy signal lamps
Before radio, and long after it, ships talked to each other by light. The classic instrument is the Aldis lamp, a hand-held signal lamp with a trigger that tilts a mirror or a shutter so the beam flashes without the bulb switching off; large ships carry shuttered searchlights that work the same way. Signalmen send at around 8 WPM, and the receiving ship acknowledges each word. Flashing light has two advantages that keep it in service: it cannot be jammed, and it cannot be intercepted by anyone not in the line of sight. The US Navy still trains signalmen in it, and NATO ships use it routinely during exercises and when radio silence is ordered.
How to read Morse code from blinking lights
Reading light Morse is the same as reading by ear, only slower: watch for the long dark gaps that separate letters, count the short and long flashes in each group, and look them up. Use the reading guide and its decoding tree. The simulator above is a good trainer: type a word, look away from the text, press "Flash it" and try to read the lamp. To decode a pattern you wrote down, paste the dots and dashes into the decoder. A "blinking Morse code translator" is just the lamp plus the decoder, both of which you have on this page.
FAQ
Frequently asked questions
How do you blink SOS in Morse code?
Three quick blinks, three long blinks (eyes closed for about a second each), three quick blinks, then a pause and repeat. The long blinks must be clearly longer than the short ones so the pattern ··· ––– ··· is obvious.
How do you communicate with a flashlight in Morse code?
A short flash is a dot, a flash about three times longer is a dash. Leave short dark gaps inside a letter, longer gaps between letters, and much longer gaps between words. Send slowly (5–8 words per minute), aim the light directly at the receiver, and use the switch or your hand to make clean flashes.
What does 3 blinks mean in Morse code?
Three short blinks or flashes is the letter S (···). Three long ones is O (–––). On their own, three blinks are not a distress signal; SOS needs all nine elements: three short, three long, three short.
Can you send Morse code with your phone's flashlight?
Yes. Toggle the torch manually at a slow speed, or use the lamp simulator on this page: type the message, press "Flash it" and hold the screen toward the receiver. For a brighter signal, show a white screen at full brightness and cover it with your hand.
How fast is Morse code sent by light?
Much slower than by sound. Naval signalmen typically work at about 8 words per minute, and beginners should go slower, around 5 WPM, which makes a dot roughly a quarter of a second and a dash about three quarters of a second.
Who blinked Morse code on television?
Jeremiah Denton, a US Navy pilot held prisoner in North Vietnam, blinked T-O-R-T-U-R-E during a 1966 propaganda interview. The message was decoded by US intelligence and confirmed that prisoners were being tortured.
Flash your own message
Scroll up, type anything, and watch the lamp send it.